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Background: The purpose of this study was to characterize the repeatability of ectopic beats, defined by premature atrial contractions (PACs) and premature ventricular contractions (PVCs), on ambulatory electrocardiogram (aECG) monitoring and evaluate the effect of length of aECG monitoring on the repeatability estimates.Methods: This analysis includes 95 randomly selected participants from the Atherosclerosis Risk in Communities Study (ARIC; 2011-2013). The participants wore a Holter monitor for two, 48-hr periods separated by a mean of 38 days following an identical, standardized protocol. We divided each 48-hr recording into 3-, 6-, 12-, and 24-hr recording periods and calculated intraclass correlation coefficients (ICCs) for PACs and PVCs and also as a percentage of the corresponding total of recorded beats per hour among these periods.Results: All participants had ≥1 PAC during the 48-hr recordings, and only two participants had no PVCs. ICCs were >0.83 for all indices and recording lengths ≥12 hrs. ICCs were intermediate for 6-hr recordings (range 0.80-0.83) and lower for 3-hr recordings (range 0.74-0.80). The ratio of the between- to within-participant variation increased with recording length.Conclusion: Repeatability of PACs and PVCs was excellent for recording lengths of 6-24 hr and fair for 3 hr. Repeatability varies over shorter duration recordings within the 48-hr recording period, and thus the present results have implications for detection algorithms for ectopic beats and can facilitate epidemiologic and clinical applications in which knowledge of measurement variability and misclassification are needed. [ABSTRACT FROM AUTHOR]

The article discusses various ways to appropriately interpret data in clinical trial registries. It highlights the important features of figures that are commonly used by medical researchers. Accordingly, it aims to convey the distinct attributes of diagrams that could possibly emphasize an impression that is consistent with valid trial conclusions. Figures sampled include flow diagrams, Kaplan-Meier plots, and forest plots.

We consider efficient study designs to estimate sensitivity and specificity of a candidate diagnostic or screening test. Our focus is the setting in which the candidate test is inexpensive to administer compared to evaluation of disease status, and the test results, available in a large cohort, can be used as a basis for sampling subjects for verification of disease status. We examine designs in which disease status is verified in a sample chosen so as to optimize estimation of either sensitivity or specificity. We then propose a sequential design in which the first step of sampling is conducted to efficiently estimate specificity. If the candidate test is determined to be of sufficient specificity, then step two of sampling is conducted to estimate sensitivity. We propose estimators based on this sequential sampling scheme, and show that the performance of these estimators is excellent. We develop sample size calculations for the sequential design, and show that this design, in most situations, compares favourably in terms of expected sample size to a fixed size design. Copyright © 2005 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]